1. Field of the Invention
The invention relates to an arrangement for determining a characteristic variable of a fluid. Furthermore, the invention relates to a sensor device for use in such an arrangement and more particularly to the use of such an arrangement in a motor vehicle.
2. Prior Art
The determination of a characteristic variable of a fluid is highly significant in the field of automobiles to sense properties of fuels, lubricants, and other operating media. For example, early detection of a critical decrease in viscosity and therefore in the lubrication capability of an oil can make it possible to determine that it will be necessary to replace the oil to ensure fault-free operation of an internal combustion engine. Furthermore, the viscosity can provide information about aging of oil and the mixing ratio of fuel mixtures, for example gasoline-ethanol or biodiesel mixtures, in particular rapeseed oil methyl ester mixtures. Other characteristic variables, a current flow rate of a fluid in a lubricant circuit or a coolant circuit are also significant.
Methods for determining a viscosity comprise, inter alia, methods for determining a dielectric constant, ultrasonic methods or simple computer-implemented calculation methods which determine the wear of an engine oil on the basis of a use time, engine parameters employed, measured temperatures and similar values.